One problem concerned with motors of the above type is the rather high sound level emanating from the pressure pulses in the exhaust air leaving the cylinder through the outlet ports in the cylinder. This problem can be and has been dealt with by fitting suitable exhaust silencers. However, silencers often generate further problems due to required extra space, particularly at portable power tools where the available space is very small. Providing an internal silencer, normally in the form of one or more extra expansion volumes, means a larger and more bulky tool housing. Fitting an external silencer means a device protruding from the housing and causing a more awkward handling of the tool.